<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>缓存全局变量</title>
  </head>
  <body>
    <input type="text" value="btn" id="btn1" />
    <input type="text" value="btn" id="btn2" />
    <input type="text" value="btn" id="btn3" />
    <input type="text" value="btn" id="btn4" />
    <p>1111</p>
    <input type="text" value="btn" id="btn5" />
    <input type="text" value="btn" id="btn6" />
    <p>2222</p>
    <input type="text" value="btn" id="btn7" />
    <input type="text" value="btn" id="btn8" />
    <p>333</p>
    <input type="text" value="btn" id="btn9" />
    <input type="text" value="btn" id="btn10" />

    <script>
      function getBtn() {
        let oBtn1 = document.getElementById("btn1");
        let oBtn3 = document.getElementById("btn3");
        let oBtn5 = document.getElementById("btn5");
        let oBtn7 = document.getElementById("btn7");
        let oBtn9 = document.getElementById("btn9");
      }

      function getBtn2() {
        let obj = document;
        let oBtn1 = obj.getElementById("btn1");
        let oBtn3 = obj.getElementById("btn3");
        let oBtn5 = obj.getElementById("btn5");
        let oBtn7 = obj.getElementById("btn7");
        let oBtn9 = obj.getElementById("btn9");
      }
    </script>
  </body>
</html>
